In vitro studies are an essential component of the initial screening for any anti-cancer therapy, allowing for high-throughput, cost-efficient exploration of potential therapeutics. However, traditional in vitro cell culture on two-dimensional (2D) tissue culture substrates fails to simulate the structure of the tumor microenvironment (TME) present in vivo (i.e., complex cell-cell organization and extracellular matrix (ECM)-cell interactions, which have significant effects on cell phenotype and malignancy). Cells in 2D culture are forced to adhere to a rigid surface and are geometrically constrained, adopting a flat morphology which alters the cytoskeleton regulation that is important in intracellular signaling, and consequently can affect cell growth, migration, and apoptosis. Moreover, organization of the ECM, which is essential to cell differentiation, proliferation, and gene expression, is absent in 2D cultured tumor cell models. These limitations of 2D cultures often result in biological responses to drugs and potentially curative treatments in vitro strikingly different from what is observed in vivo. The ideal in vitro TME model should provide a platform for in vitro drug screening that will better translate to in vivo testing by mimicking both the spatial arrangement of cells and ECM signaling found in tumors in vivo, resulting in the expression of the native in vivo phenotype in these cells.
Often in vitro results often do not translate well to in vivo systems. As a result, costly in vivo animal models remain the most sophisticated and faithful models of the disease. The development of anticancer drugs has been hindered by the lack of effective tumor models that closely mimic the human disease.
Three-dimensional (3D) culture systems are designed to bridge the gap between in vitro and in vivo cancer models. These 3D systems are intended to increase cancer cell malignancy and retain the in vivo phenotype by mimicking the structure of the tumor microenvironment. Natural extracellular matrix materials such as collagen, fibrin, and the commercially available Matrigel matrix (BD Biosciences) have been used, but these animal-source products are expensive, and can potentially transmit pathogens. Synthetic polymers such as poly(lactide-co-glycolide) (PLGA) have also been studied, but they can release acidic degradation products that are toxic to cells, and negatively affect experimental results.
A need exists for improved in vitro models of human cancer that will allow researchers to reduce in vivo experiments by in vitro pre-testing that will defray costs, shorten experimental time, provide a much more controllable environment, and reduce loss of animal life. The present invention seeks to fulfill this need and provides further related advantages.